JP4299360B2 - Piezoelectric element and liquid ejection apparatus using the same - Google Patents

Description

  The present invention relates to a piezoelectric element in which a piezoelectric film is formed on a substrate via an electrode by a vapor phase growth method using plasma, and a liquid discharge apparatus using the piezoelectric element.

  A piezoelectric element having a piezoelectric film having a piezoelectric property that expands and contracts as the electric field application intensity increases and decreases, and an electrode that applies an electric field to the piezoelectric film is used as an actuator mounted on an ink jet recording head. Yes. Currently, various types of electronic components are required to be smaller and have higher performance, and even in an ink jet recording head, it is required to reduce the size of piezoelectric elements so that they can be mounted at high density in order to achieve higher image quality.

  In miniaturization of a piezoelectric element, it is desirable that the piezoelectric film used for the piezoelectric element is as thin as possible and has good piezoelectricity because of processing accuracy. However, in the piezoelectric film obtained by the conventional sintering method, as the film thickness decreases, the film thickness approaches the size of the crystal grains constituting the piezoelectric film, so the influence of the crystal grain size and shape on the piezoelectric performance. Cannot be neglected, performance variations and deterioration are likely to occur, and it is difficult to obtain sufficient performance. In order to avoid the influence of such crystal grains, thinning of the piezoelectric film by a vapor phase growth method such as a sputtering method or PVD (physical vapor deposition method) has been studied as a thin film forming technique replacing the sintering method.

  However, even when the piezoelectric film is thinned by the vapor phase growth method, due to the problem of crystal grain boundaries and crystal orientation, the piezoelectric performance varies greatly compared to the bulk sintered body, and a piezoelectric film having sufficient piezoelectric performance is obtained. Since it is difficult to obtain, attempts have been made to optimize the crystal structure.

  In Patent Document 1, a majority of crystal grains constituting the lead-containing piezoelectric film have a columnar structure, and the composition of constituent elements in the film thickness direction is changed continuously or stepwise. A piezoelectric element is disclosed.

Patent Document 2 discloses a piezoelectric element in which the piezoelectric film is a two-layered piezoelectric laminated film, and the lower layer of the piezoelectric laminated film is an orientation control layer having good adhesion to the lower electrode.
Japanese Patent No. 3705089 JP 2005-203725 A

  Although it is described that the piezoelectric element of Patent Document 1 has good piezoelectric characteristics and can be reduced in size, precise control of applied voltage is required to change the composition of the piezoelectric film in the film thickness direction. The film formation process is complicated.

  Moreover, although it is described that the piezoelectric element of patent document 2 has a large piezoelectric characteristic and high durability by providing an orientation control layer having high adhesion, each of the piezoelectric films has a two-layer structure. It is necessary to change the target composition and film formation conditions in accordance with the piezoelectric film, and the process is complicated.

  The present invention has been made in view of the above circumstances, and has good piezoelectric characteristics in a piezoelectric element in which a piezoelectric film is formed on a substrate via an electrode by a vapor phase growth method using plasma, An object of the present invention is to provide a piezoelectric element that can be manufactured by a simple process.

  The piezoelectric element of the present invention is a piezoelectric element in which a piezoelectric film is formed on a substrate via an electrode by a vapor phase growth method using plasma, and the piezoelectric film is one or more represented by the following general formula: It is a kind of perovskite type oxide (which may contain inevitable impurities) and consists of a columnar structure film consisting of a large number of columnar crystals extending in a non-parallel direction to the substrate surface, and is observed on the surface of the columnar structure film The end faces of a large number of columnar crystals have a size in which the diameter of the minimum circumscribed circle of the end faces is distributed from 100 nm or less to 500 nm or more, and the diameter of the circumscribed circle is 20 nm or less. % Or more and 5% or more of 500 nm or more, and the surface roughness Ra of the columnar structure film is 10 nm or less.

Pb (Ti _x , Zr _y , M _z ) O ₃
(In the above formula, M is at least one metal selected from the group consisting of Sn, Nb, Ta, Mo, W, Ir, Os, Pd, Pt, Re, Mn, Co, Ni, V, and Fe. Element, 0 <x <1, 0 <y <1, 0 ≦ z <1, x + y + z = 1.)
In the above formula, Pb is an A site element, and Ti, Zr, and M are B site elements. In this specification, the molar ratio of Pb, which is an A site element, and an oxygen atom, and the molar ratio of a B site element, to an oxygen element are basically 1: 3. : It may deviate from 3. For the B site composed of a plurality of elements, x + y + z, which is the sum of the number of moles of each B site element when the number of moles of oxygen atoms is 3, is standard, but within the range where a perovskite structure can be taken. Means that it may deviate from 1.

The vapor phase growth method is preferably a method in which a film is formed at a film forming temperature of less than 550 ° C., and a plasma potential Vs (V) and a floating potential Vf (V) in the plasma during film formation It is preferable that the film is formed under the condition of Vs−Vf (V), which is a difference of 10V to 30V.
In this specification, the “film formation temperature” means the center temperature of the substrate on which film formation is performed.

  The vapor phase growth method is preferably any one of a sputtering method, an ion plating method, and a plasma CVD method.

  In the piezoelectric element of the present invention, the columnar structure film preferably has a thickness of 1 μm or more.

  A liquid discharge apparatus of the present invention includes the piezoelectric element of the present invention and a liquid discharge member provided integrally or separately on the substrate of the piezoelectric element. The liquid discharge member stores liquid. A liquid storage chamber and a liquid discharge port through which the liquid is discharged from the liquid storage chamber.

  In the piezoelectric element of the present invention, the piezoelectric film is formed by a vapor phase growth method using plasma, and one or more perovskite oxides (inevitable impurities) of the lead zirconate titanate system represented by the above general formula. The end faces of a large number of columnar crystals observed on the surface of the columnar structure film have a diameter of the minimum circumscribed circle of the end faces ranging from 100 nm or less to 500 nm or more. The diameter of the circumscribed circle is 20% or more and the diameter of the circumscribed circle is 20% or more and 500% or more, and the surface roughness Ra of the columnar structure film is 10 nm or less. It is supposed to be.

  According to such a configuration, since the surface roughness Ra is small, electric field concentration hardly occurs, and deterioration of the piezoelectric body due to electric field concentration can be suppressed. In addition, the smaller the Ra, the better the patterning accuracy in the subsequent process at the time of device fabrication, so the in-plane driving uniformity is good.

  In addition, the piezoelectric film of the piezoelectric element of the present invention has a wide distribution of crystal grain sizes, and the entire piezoelectric film is indefinite. Crystals with a large grain size are considered to be easily restricted in piezoelectricity by in-plane stress, etc., but in the present invention, they are mixed with crystals with a small grain size and the stress is easily relaxed, so the piezoelectric performance is limited. It will not be done.

  Furthermore, since it is not necessary to make the particle size substantially uniform, a complicated process such as changing the composition of the piezoelectric film in the film thickness direction or providing an orientation control layer is not required.

  Therefore, according to the present invention, it is possible to provide a piezoelectric element that has high element reliability, good piezoelectric characteristics, and can be manufactured by a simple process by vapor phase growth using plasma.

"Piezoelectric element"
With reference to FIG. 1, the structure of a piezoelectric element and an ink jet recording head (liquid ejecting apparatus) according to an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view of a main part of an ink jet recording head. In order to facilitate visual recognition, the scale of the constituent elements is appropriately changed from the actual one.

The ink jet recording head (liquid ejecting apparatus) 3 of the present embodiment roughly ejects ink to the outside from the ink chamber (liquid storing chamber) 21 in which ink is stored and the ink chamber 21 on the back surface of the piezoelectric actuator 2. An ink nozzle (liquid storage and discharge member) 20 having an ink discharge port (liquid discharge port) 22 is attached.
In the ink jet recording head 3, the electric field strength applied to the piezoelectric element 1 is increased / decreased to expand / contract the piezoelectric element 1, thereby controlling the ejection of the ink from the ink chamber 21 and the ejection amount.

  In the piezoelectric actuator 2, a vibration plate 16 that vibrates due to expansion and contraction of the piezoelectric film 13 is attached to the back surface of the substrate 11 of the piezoelectric element 1. The piezoelectric actuator 2 is also provided with a control means 15 such as a drive circuit for driving the piezoelectric element 1.

  Instead of attaching the diaphragm 16 and the ink nozzle 20 which are members independent of the substrate 11, a part of the substrate 11 may be processed into the diaphragm 16 and the ink nozzle 20. For example, the ink chamber 21 can be formed by etching the substrate 11 from the back side, and the diaphragm 16 and the ink nozzle 20 can be formed by processing the substrate itself.

  The piezoelectric element 1 is an element in which a lower electrode layer 12, a piezoelectric film 13, and an upper electrode layer 14 are sequentially laminated on the surface of a substrate 11. The piezoelectric film 13 is composed of a lower electrode layer 12 and an upper electrode layer 14. An electric field is applied in the film thickness direction.

In the piezoelectric element 1 of this embodiment, the substrate 11 is not particularly limited, and examples thereof include silicon, glass, stainless steel (SUS), yttrium stabilized zirconia (YSZ), SrTiO ₃ , alumina, sapphire, and silicon carbide. . As the substrate 11, a laminated substrate such as an SOI substrate in which a SiO ₂ film and a Si active layer are sequentially laminated on a silicon substrate may be used. Further, a buffer layer for improving the lattice matching, an adhesion layer for improving the adhesion between the electrode and the substrate, or the like may be provided between the substrate 11 and the lower electrode layer 12.

The main components of the lower electrode 12 and the upper electrode 14 are not particularly limited, and metals or metal oxides such as Au, Pt, Ir, IrO ₂ , RuO ₂ , LaNiO ₃ , and SrRuO ₃ and combinations thereof, and Cr, W, Ti, Al, Fe, Mo, In, Sn, Ni, Cu, Co, and other non-noble metals such as Ta, and at least one metal selected from the group consisting of these alloys, and these And the like.
The thicknesses of the lower electrode 12 and the upper electrode 14 are not particularly limited and are preferably 50 to 500 nm.

The piezoelectric film 13 is made of a perovskite oxide represented by the following general formula (may contain inevitable impurities).
Pb (Ti _x , Zr _y , M _z ) O ₃
(In the above formula, M is at least one metal selected from the group consisting of Sn, Nb, Ta, Mo, W, Ir, Os, Pd, Pt, Re, Mn, Co, Ni, V, and Fe. Element, 0 <x <1, 0 <y <1, 0 ≦ z <1, x + y + z = 1.)

  Examples of the perovskite oxide represented by the above general formula include lead titanate, lead zirconate titanate (PZT), lead zirconate, lead zirconate titanate niobate, and the like.

  In this embodiment, the piezoelectric film 13 is formed on the substrate 11 via the lower electrode 12 by a vapor phase growth method using plasma, and has a number of columnar shapes extending in a non-parallel direction with respect to the substrate surface. It is a columnar structure film made of a crystal body 17.

  FIG. 2A shows a partially enlarged perspective view (schematic diagram) showing the structure of the piezoelectric film 13. The columnar structure film (piezoelectric film) 13 has a surface roughness Ra of the surface 13s of 10 nm or less, and a large number of the columnar crystal bodies 17 forming the columnar structure film 13 have the minimum circumscribing of the end face 17s observed on the surface 13s. The diameter r of the circle (FIG. 2 (b)) has a size distributed from 100 nm or less to 500 nm or more, and the circumscribed circle has a diameter of 100 nm or less and 20% or more and 500 nm or more. Is an indefinite shape including 5% or more (see FIGS. 7 and 8 of the first embodiment).

  The surface roughness Ra is an arithmetic average surface roughness, and it is preferable that the surface roughness Ra be small. When Ra is a value larger than 10 nm, the durability is deteriorated due to the concentration of the electric field at the time of driving or the accuracy in patterning is increased. This causes problems such as worsening and in-plane driving uniformity. Ra is preferably 8 nm or less, and more preferably 6 nm or less.

  In general, when a film made of a perovskite oxide is observed on the film surface, it has a square shape in the (100) orientation and (001) orientation, a quadrangular pyramid shape in the (111) orientation, and a roof shape in the (110) orientation. (See FIG. 14 of Comparative Example 1). However, on the film surface of the piezoelectric film (columnar structure film) 13 of the present embodiment, the end face shape of the many columnar crystal bodies 17 is indefinite as described above, and such a general perovskite oxide film is used. The observed columnar crystal 17 is 10% or less of the whole.

  The method for forming the piezoelectric film 13 is not particularly limited as long as it is a vapor phase growth method using plasma, and examples thereof include a sputtering method, an ion plating method, and a plasma CVD method.

  When the piezoelectric film 13 is formed by the vapor phase growth method as described above, for example, the film formation temperature is preferably 400 ° C. or higher and lower than 550 ° C. Below 400 ° C., it is difficult to stably grow perovskite crystals. On the other hand, in order to obtain the piezoelectric film 13 composed of the columnar structure film in which the end surfaces of the many columnar crystals 17 are indefinite, the film formation temperature is preferably less than 550 ° C. Even when the temperature is 550 ° C. or higher, the perovskite structure piezoelectric film 13 can be formed. However, when the film formation temperature is high, the structure tends to be stable at that temperature. In other words, the particle diameters are easily aligned.

  When the film is formed at 550 ° C. or higher, the particle diameters are likely to be uniform as described above. However, since the film formation temperature is high, the surface roughness Ra is likely to increase. Cracks and the like are likely to occur in the film due to the stress caused by the difference in thermal expansion coefficient with the piezoelectric film 13. Therefore, it is difficult to obtain a film having good piezoelectric performance unless a process for changing the composition of the piezoelectric film in the film thickness direction is provided as in Patent Documents 1 and 2.

  The film thickness of the piezoelectric film 13 is not particularly limited, but it is preferably thinner in terms of thickness reduction. If it is too thin, sufficient piezoelectric performance cannot be obtained due to the influence of stress from the interface between the substrate and the film. It is preferable.

  In the case where the piezoelectric film 13 is formed by a vapor phase growth method using plasma such as a sputtering method, the present inventor determines the difference between the plasma potential Vs (V) in the plasma at the time of film formation and the floating potential Vf (V). It has been found that it is preferable to form a film under a condition where a certain Vs-Vf (V) is 10 to 30V.

In this specification, the “plasma potential Vs and floating potential Vf” are measured by a single probe method using a Langmuir probe. The floating potential Vf is measured in as short a time as possible so that the tip of the probe is placed in the vicinity of the substrate (about 10 mm from the substrate) so as not to include errors due to the film being deposited on the probe. To do.
The potential difference Vs−Vf (V) between the plasma potential Vs and the floating potential Vf can be directly converted into the electron temperature (eV). This corresponds to an electron temperature of 1 eV = 11600 K (K is an absolute temperature).

FIG. 3 shows that the inventor changed the film formation temperature Ts and Vs−Vf by the sputtering method to obtain PZT (Pb _1.3 Zr _0.52 Ti _0.48 O ₃ ) or Nb—PZT (Pb _1.3 Zr). ₄ shows the result of observing the surface shape from the SEM image of the surface of the piezoelectric film by forming a piezoelectric film using a target of _0.43 Ti _0.44 Nb _0.13 O ₃ ). In FIG. 3, the plot at the film formation temperature Ts = 525 ° C. is an Nb-PZT film, and the other plots are PZT films.

  In FIG. 3, the surface roughness Ra of the surface 13s is 10 nm or less, and the diameter of the circumscribed circle of the end face 17s of the columnar crystal 17 observed on the surface 13s has a size distributed from 100 nm or less to 500 nm or more. In addition, the plots of ● are shown only for those that are indeterminate including those having a circumscribed circle diameter of 20% or more and 500 nm or more having a diameter of 100 nm or less and 5% or more.

  FIG. 3 shows the surface of the piezoelectric film 13 in which the PZT film or the Nb-PZT film is formed under the conditions that Vs-Vf is 10 V or more and 30 V or less and the film formation temperature Ts is 400 ° C. or more and less than 550 ° C. It is shown that the end faces 17s of a large number of columnar crystals 17 observed at 13s are indefinite as described above.

  In general, when PZT bulk ceramics is formed by a metallurgical technique such as sintering, the formation temperature is 800 ° C. or higher, but the formation temperature can be increased by using non-thermal equilibrium plasma such as sputtering. Is known to drop significantly. At such a low formation temperature, there is a possibility that the crystal and the internal structure take a non-thermal equilibrium state instead of the conventional thermal equilibrium state. A film formed at a temperature of 550 ° C. or lower as described above is considered to have properties different from metallurgical bulk ceramics.

  In the piezoelectric element 1 of the present embodiment, the piezoelectric film 13 is formed by a vapor phase growth method using plasma, and one or more perovskite oxides of the lead zirconate titanate type represented by the above general formula The end surface 17s of a large number of columnar crystals 17 observed on the surface 13s of the columnar structure film 13 is composed of a columnar structure film 13 (which may contain inevitable impurities), and the diameter of the minimum circumscribed circle of the end surface 17s. Having a size distributed over 100 nm or less to 500 nm or more, and the diameter of the circumscribed circle is 100 nm or less, including 20% or more, and 500 nm or more containing 5% or more. 13 has a surface roughness Ra of 10 nm or less.

  According to such a configuration, since the surface roughness Ra is small, electric field concentration hardly occurs, and deterioration of the piezoelectric film due to electric field concentration can be suppressed. In addition, the smaller the Ra, the better the patterning accuracy in the subsequent process at the time of device fabrication, so the in-plane driving uniformity is good.

  In addition, the piezoelectric film 13 of the piezoelectric element 1 has a wide distribution of crystal grain sizes, and the entire piezoelectric film is indefinite. Crystals with a large grain size are considered to be easily restricted in piezoelectricity by in-plane stress, etc., but in the present invention, they are mixed with crystals with a small grain size and the stress is easily relaxed, so the piezoelectric performance is limited. It will not be done.

  Furthermore, since it is not necessary to make the particle sizes substantially uniform, a complicated process such as changing the composition of the piezoelectric film 13 in the film thickness direction or providing an orientation control layer is not required.

  Therefore, according to the present invention, it is possible to provide a piezoelectric element 1 having high element reliability, good piezoelectric characteristics, and capable of being manufactured by a simple process, by vapor phase growth using plasma. .

"Inkjet recording device"
With reference to FIG. 4 and FIG. 5, a configuration example of an ink jet recording apparatus including the ink jet recording head 3 of the above embodiment will be described. 4 is an overall view of the apparatus, and FIG. 5 is a partial top view.

  The illustrated ink jet recording apparatus 100 includes a printing unit 102 having a plurality of ink jet recording heads (hereinafter simply referred to as “heads”) 3K, 3C, 3M, and 3Y provided for each ink color, and each head 3K, An ink storage / loading unit 114 that stores ink to be supplied to 3C, 3M, and 3Y, a paper feeding unit 118 that supplies recording paper 116, a decurling unit 120 that removes curling of the recording paper 116, and a printing unit An adsorption belt conveyance unit 122 that conveys the recording paper 116 while maintaining the flatness of the recording paper 116, and a print detection unit that reads a printing result by the printing unit 102. 124 and a paper discharge unit 126 that discharges printed recording paper (printed matter) to the outside.

  The heads 3K, 3C, 3M, and 3Y that form the printing unit 102 are the ink jet recording heads 3 of the above-described embodiment.

In the decurling unit 120, heat is applied to the recording paper 116 by the heating drum 130 in the direction opposite to the curl direction, and the decurling process is performed.
In the apparatus using roll paper, as shown in FIG. 4, a cutter 128 is provided at the subsequent stage of the decurling unit 120, and the roll paper is cut into a desired size by this cutter. The cutter 128 includes a fixed blade 128A having a length equal to or larger than the conveyance path width of the recording paper 116, and a round blade 128B that moves along the fixed blade 128A. The fixed blade 128A is provided on the back side of the print. The round blade 128B is arranged on the print surface side with the conveyance path interposed therebetween. In an apparatus using cut paper, the cutter 128 is unnecessary.

  The decurled and cut recording paper 116 is sent to the suction belt conveyance unit 122. The suction belt conveyance unit 122 has a structure in which an endless belt 133 is wound between rollers 131 and 132, and at least portions facing the nozzle surface of the printing unit 102 and the sensor surface of the printing detection unit 124 are horizontal ( Flat surface).

  The belt 133 has a width that is wider than the width of the recording paper 116, and a plurality of suction holes (not shown) are formed on the belt surface. An adsorption chamber 134 is provided at a position facing the nozzle surface of the printing unit 102 and the sensor surface of the print detection unit 124 inside the belt 133 that is stretched between the rollers 131 and 132. The recording paper 116 on the belt 133 is sucked and held by suctioning at 135 to make a negative pressure.

  When the power of a motor (not shown) is transmitted to at least one of the rollers 131 and 132 around which the belt 133 is wound, the belt 133 is driven in the clockwise direction in FIG. 4 and is held on the belt 133. The recording paper 116 is conveyed from left to right in FIG.

Since ink adheres to the belt 133 when a borderless print or the like is printed, the belt cleaning unit 136 is provided at a predetermined position outside the belt 133 (an appropriate position other than the print region).
A heating fan 140 is provided on the upstream side of the printing unit 102 on the paper conveyance path formed by the suction belt conveyance unit 122. The heating fan 140 heats the recording paper 116 by blowing heated air onto the recording paper 116 before printing. Heating the recording paper 116 immediately before printing makes it easier for the ink to dry after landing.

  The printing unit 102 is a so-called full line type head in which line type heads having a length corresponding to the maximum paper width are arranged in a direction (main scanning direction) perpendicular to the paper feed direction (see FIG. 5). Each of the print heads 3K, 3C, 3M, and 3Y is a line-type head in which a plurality of ink discharge ports (nozzles) are arranged over a length exceeding at least one side of the maximum-size recording paper 116 targeted by the ink jet recording apparatus 100. It is configured.

  Heads 3K, 3C, 3M, and 3Y corresponding to the respective color inks are arranged in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side along the feeding direction of the recording paper 116. ing. A color image is recorded on the recording paper 116 by ejecting the color ink from each of the heads 3K, 3C, 3M, 3Y while conveying the recording paper 116.

The print detection unit 124 includes a line sensor that images the droplet ejection result of the print unit 102 and detects ejection defects such as nozzle clogging from the droplet ejection image read by the line sensor.
A post-drying unit 142 including a heating fan or the like for drying the printed image surface is provided at the subsequent stage of the print detection unit 124. Since it is preferable to avoid contact with the printing surface until the ink after printing is dried, a method of blowing hot air is preferred.

  A heating / pressurizing unit 144 is provided downstream of the post-drying unit 142 in order to control the glossiness of the image surface. The heating / pressurizing unit 144 presses the image surface with a pressure roller 145 having a predetermined surface irregularity shape while heating the image surface, and transfers the irregular shape to the image surface.

The printed matter obtained in this manner is outputted from the paper output unit 126. It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. In the ink jet recording apparatus 100, there is provided sorting means (not shown) for switching the paper discharge path in order to select the print product of the main image and the print product of the test print and send them to the discharge units 126A and 126B. It has been.
When the main image and the test print are simultaneously printed on a large sheet of paper, the cutter 148 may be provided to separate the test print portion.
The ink jet recording apparatus 100 is configured as described above.

Examples and comparative examples according to the present invention will be described.
Example 1
A 10-nm thick Ti adhesion layer and a 150-nm thick Ir lower electrode were formed on a 6-inch SOI substrate by sputtering at a substrate temperature of 350 ° C. Next, Pb _1.3 (Zr _0.52 Ti _0.48 ) ₀ under conditions of a degree of vacuum of 0.5 Pa, an Ar / O ₂ mixed atmosphere (O ₂ volume fraction of 1.0%), and a film formation temperature of 480 ° C. _A piezoelectric film (Nb-PZT film) made of Nb-doped PZT having a thickness of 4 μm was formed by sputtering using a _.9 Nb _0.10 O ₃ target. At this time, the substrate was placed in a floating state, and a film was formed by arranging ground at a location apart from the substrate, not between the target and the substrate. When the plasma potential Vs and the floating potential (potential in the vicinity of the substrate (= about 10 mm from the substrate)) Vf during the film formation were measured, Vs−Vf (V) = about 30. The input power was 500 W, and the distance between the substrate targets was 60 mm.

  The X-ray diffraction (XRD) measurement result of the obtained film is shown in FIG. 6, and the surface SEM image is shown in FIG. In addition, FIG. 8 shows an image pattern of crystal grains measured by EBSD (backscattered electron diffraction pattern method) in order to make the crystal grains easy to see. As can be seen from FIG. 6, the obtained film was a perovskite single phase (100) preferentially oriented film (orientation ratio 90% or more). 7 and 8, the surface of the obtained film is substantially smooth, and when the size of the surface of the crystal grain in the field of view is measured, the diameter of the smallest peripheral circle of the crystal grain is 50 nm to 1200 nm. A wide range of crystal grains was observed. The particle size distribution obtained with the diameter of the outer circumference circle as the particle size is shown in FIG.

  Moreover, the cross-sectional SEM photograph of the film thickness direction of the obtained film | membrane is shown in FIG. Moreover, the image pattern of the crystal grain of the film | membrane cross section measured by EBSD is shown in FIG. 10 and 11, it was confirmed that the crystal grains of the obtained film consisted of columnar crystals. Ra of the obtained film was measured with a surface level meter based on JIS B0601-1994. Ra of the obtained film | membrane was 5.3 nm and was favorable.

  Next, a Pt upper electrode is formed with a thickness of 100 nm on the Nb-PZT piezoelectric film by sputtering, patterned by lift-off, and further, the back side of the SOI substrate is dry-etched to form a 500 μm square ink chamber. A 6 μm-thick vibration plate and an ink nozzle having an ink chamber and an ink discharge port were formed by processing itself to obtain an ink jet recording head of the present invention.

On the other hand, a voltage was applied, and bipolar polarization-electric field characteristics (PE hysteresis characteristics) were measured. Measurement was performed with the maximum electric field strength set to V = 170 kV / cm under the condition of a frequency of 5 Hz. The PE hysteresis curve is shown in FIG. From FIG. 12, it was confirmed that good ferroelectricity was exhibited.
Next, when the displacement of the piezoelectric film was measured with a laser Doppler vibrometer and the piezoelectric constant was calculated with ANSYS (Young's modulus obtained from the resonance point was 50 MPa), the obtained piezoelectric constant d ₃₁ was 260 pm / V. It was high and good.

  Further, this film was subjected to a long-term driving test at 40 ° C. and 80% RH (relative humidity). In the driving of 100 billion dots, no change in displacement was observed, and the durability was good.

(Comparative Example 1)
An Nb-PZT film was formed in the same manner as in Example 1 except that the film formation temperature was 550 ° C., and evaluation was performed by measuring XRD and surface SEM images of the film obtained in the same manner.

  The X-ray diffraction (XRD) measurement result of the obtained film is shown in FIG. 13, and the surface SEM image is shown in FIG. As can be seen from FIG. 13, the obtained film was a perovskite single phase (100) preferentially oriented film (orientation ratio of 90% or more). Further, in the SEM image of FIG. 14, about 3 to 5% of a columnar crystal having a square shape, a quadrangular pyramid shape, or a roof shape grain shape observed on the surface of a general perovskite oxide film was observed.

  Further, when the size of the surface of the crystal grain in the field of view was measured, the diameter of the smallest outer circumference of the crystal grain was in the range of 20 nm to 300 nm, and the grain size distribution was relatively narrow. Further, when Ra was measured in the same manner as in Example 1, it was 11 nm, which was large.

  Next, in the same manner as in Example 1, an ink jet recording head according to the present invention was obtained by forming a 6 μm thick diaphragm, an ink chamber having a 500 μm square ink chamber, and an ink discharge port with a Pt upper electrode. It was.

  On the other hand, as in Example 1, bipolar polarization-electric field characteristics (PE hysteresis characteristics) were measured. The PE hysteresis curve is shown in FIG. From FIG. 15, it was confirmed that good ferroelectricity was exhibited.

Next, when the displacement of the piezoelectric film was measured with a laser Doppler vibrometer and the piezoelectric constant was calculated with ANSYS (Young's modulus obtained from the resonance point was 50 MPa), the obtained piezoelectric constant d ₃₁ was 160 pm / V. And lower than that of Example 1.

  Further, this film was subjected to a driving test at 40 ° C. and 80% RH in the same manner as in Example 1. A drop in displacement was observed from about 200 mm dots, and the durability was low.

  The piezoelectric element of the present invention is preferably used for an ink jet recording head, a magnetic recording / reproducing head, a MEMS (Micro Electro-Mechanical Systems) device, a micro pump, an ultrasonic probe mounted on an ultrasonic probe, and a diaphragm. it can.

1 is a cross-sectional view of a principal part showing the structure of a piezoelectric element according to an embodiment of the present invention and an ink jet recording head (liquid ejection apparatus) including the same (A) is the elements on larger scale which show the structure of the piezoelectric film of embodiment which concerns on this invention, (b) is a figure which shows the diameter of the circumcircle of the end surface in the piezoelectric film surface of a columnar crystal body A graph plotting the results of observing the surface shape of the piezoelectric film with the film forming temperature Ts as the horizontal axis and Vs−Vf as the vertical axis 1 is a diagram illustrating a configuration example of an ink jet recording apparatus including the ink jet recording head of FIG. Partial top view of the ink jet recording apparatus of FIG. XRD pattern of main piezoelectric film obtained in Example 1 Surface SEM image of the piezoelectric film in FIG. Image pattern of crystal grains by EBSD on the piezoelectric film surface of FIG. The figure which shows the particle size distribution in the piezoelectric film surface analyzed from the surface SEM image of FIG. Cross-sectional SEM photograph of the film thickness direction of the piezoelectric film of FIG. Image pattern of crystal grain by EBSD of the piezoelectric film cross section of FIG. Polarization-electric field hysteresis curve of the piezoelectric film in FIG. XRD pattern of main piezoelectric film obtained in Comparative Example 1 Surface SEM image of the piezoelectric film of FIG. Polarization-electric field hysteresis curve of the piezoelectric film in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Piezoelectric actuator 3, 3K, 3C, 3M, 3Y Liquid discharge apparatus (inkjet recording head)
12, 14 Electrode 13 Piezoelectric film (columnar structure film)
13s surface of piezoelectric film 17 columnar crystal 17s end surface of columnar crystal 20 ink nozzle (liquid storage and discharge member)
21 Ink chamber (liquid storage chamber)
22 Ink ejection port (liquid ejection port)
100 Inkjet recording apparatus r The diameter of the minimum circumscribed circle of the end face on the film surface of the columnar crystal

Claims (9)

In a piezoelectric element in which a piezoelectric film is formed on a substrate via an electrode by a vapor phase growth method using plasma,
The piezoelectric film is one or a plurality of perovskite oxides (which may contain inevitable impurities) represented by the following general formula and extend in a non-parallel direction to the substrate surface It consists of a columnar structure film consisting of a body,
The end faces of the many columnar crystals observed on the surface of the columnar structure film have a size in which the diameter of the minimum circumscribed circle of the end faces is distributed from 100 nm or less to 500 nm or more, and The diameter of the circumscribed circle includes 20% or more of the diameter of 100 nm or less, and 5% or more of the diameter of 500 nm or more,
The piezoelectric element, wherein the columnar structure film has a surface roughness Ra of 10 nm or less.
Pb (Ti _x , Zr _y , M _z ) O ₃
(In the above formula, M is at least one metal selected from the group consisting of Sn, Nb, Ta, Mo, W, Ir, Os, Pd, Pt, Re, Mn, Co, Ni, V, and Fe. Element, 0 <x <1, 0 <y <1, 0 ≦ z <1, x + y + z = 1.)   The piezoelectric element according to claim 1, wherein the piezoelectric film has crystal orientation.   The piezoelectric element according to claim 2, wherein the piezoelectric film has a (100) -oriented crystal orientation. The piezoelectric element according to any one of claims 1 to 3, wherein the vapor deposition method forms a film under a film forming temperature of less than 550 ° C. In the vapor phase growth method, the film is formed under the condition that Vs−Vf (V), which is the difference between the plasma potential Vs (V) in the plasma during film formation and the floating potential Vf (V), is 10V to 30V. The piezoelectric element according to any one of claims 1 to 4, wherein the piezoelectric element is one. The vapor phase growth method, a sputtering method, an ion plating method, and among the plasma CVD method, a piezoelectric element according to any one of claims 1 to 5, characterized in that either. The piezoelectric element according to any one of claims 1 to 6, wherein the thickness of the columnar structure film is 1μm or more. The piezoelectric element according to claim 1-7,
A liquid ejection member provided integrally or separately on the substrate of the piezoelectric element,
The liquid ejection apparatus, wherein the liquid ejection member has a liquid storage chamber in which liquid is stored, and a liquid discharge port through which the liquid is discharged from the liquid storage chamber. Using a vapor phase growth method using plasma, the general formula Pb (Ti _x , Zr _y , M _z ) O ₃
(In the above formula, M is at least one metal selected from the group consisting of Sn, Nb, Ta, Mo, W, Ir, Os, Pd, Pt, Re, Mn, Co, Ni, V, and Fe. Element, 0 <x <1, 0 <y <1, 0 ≦ z <1, x + y + z = 1.)
A method for producing a piezoelectric film containing one or more perovskite oxides (which may contain inevitable impurities) represented by:
A method for producing a piezoelectric film, characterized in that a film is formed under conditions satisfying the following formulas (1) and (2).
400 ≦ Ts (° C.) <550 (1),
10 ≦ Vs−Vf (V) ≦ 30 (2)
(In the formulas (1) and (2), Ts (° C.) is the film forming temperature, and Vs−Vf (V) is the difference between the plasma potential Vs (V) in the plasma and the floating potential Vf (V).)